fix exception when trying berkeleydb example

CompilerException java.lang.IllegalArgumentException: No implementation of method: :open of protocol:
#'clojurewerkz.titanium.graph/TitaniumGraph found for class: nil, compiling:(graphs1.clj:10:8) 

EDIT: for clarity:
=> `(System/getProperty "java.io.tmpdir")`
"C:\\Users\\user\\AppData\\Local\\Temp\\"
=> `(System/getenv "tmp")`
"C:\\Users\\user\\AppData\\Local\\Temp"
=> `(System/getenv "temp")`
"C:\\Users\\user\\AppData\\Local\\Temp"
=> `(System/getenv "java.io.tmpdir")`
nil